Heating element



April 21, 1953 c. H. SPARKLIN ETAL 2,636,105

We; W U? z M A ril 21, 1953 c. H. SPARKLIN ET AL 2,636,106

HEATING ELEMENT Filed Dec. 31, 1948 2 Sl-IEETSSl-IEET 2 .E E,Marx-$9325. v IIIIIIIIIIIIIIIIIIIIIIIII 'IIIIIIIIII IIIIIIII/ e PatentedApr. 21, 1953 UNITED- STATES PATENT OFFICE HEATING ELEMENTv Charles H.Sparklin and Philip J More, Chicago,

111;, assignors' to-Birtman corporation of Illinois ApplicationDecember31, 19.48, Serial No. 68,588;

8 Claims.

This invention relates. to a heating element,v

efilciency. of .theinsulating material and the rigid sealing oftheresistance element within the insulating. material.

In: therpresent invention there is provided an improved heating element.comprising a metal plate having. an elongated groove therein with.

thisgroovehaving areduced and extended end.

Theresistance element. is'provided in this groove with a terminalportionthereof extending out of the reducedv end. Insulating material isarranged. withinthe groove and. surrounding the resistance element andiatube comprising woven fiber glass is arranged around this end of theresistance element. A cover. plate extends betweenthe sides of thegroove and contacts the insulating material, and. serves to hold thetube in place. This tubeof fiber glass. is held tightly in. position andserves to insulate the resistance element from the surroundingstructure. The fiber glass tube is. not only important for itsinsulating value, but. it is also very simple to slip thetube over theend of the resistance element in the manufacturing operation. In thepreferred construction there are provided thin sheets of" separateinsulating material,. such as mica, in. contact with the top and bottomsurfaces of the fiber glass tube. These sheets provide additionalinsulating'structures and are so arranged that the bottom sheet rests onthe bottom of the extended end of the groove, while the top sheet ispressed down by the cover plate.

The insulatingmaterial in the groove is preferably, but not necessarily,a powdered zirconium silicate that is tightly compressed by the coverplate. This combination of insulating'material, resistance element,hollow fiber glass tube and cover plate provides a rigid structure thatprevents shifting of the resistance element and results in anextremelylong life for the heating element.

In the preferred construction, where the heating element is used in anelectric iron, there is provided an elongated groove having rounded endsthereon together with a resistance element within the groove comprisingan elongated resistancemetal strip, either a tape or a wire;

Electric Company, a

2 wound around a solid core... This core is provided withrounded endsthat'are shaped to. bear. against the rounded ends" of the groove andlo' cate the resistance element within the groove.

This core' has the sides thereof between the rounded ends spacedinwardly, with the resistance metal strip being wound around thisportion' of the. core. In a preferred construction, each end of theresistance metal strip extends beyond the core and through a hole. oropening in one of the rounded ends. This construction aids inmaintaining the strip tightly Wound. around the core.

In the usual embodiment of the invention for use in electric irons themetal plate is provided. with a pair of converging. elongated. grooves.with a short groove connecting the converging ends of the grooves. Thereis provided apair of resistance elements inthe grooves with theresistance. metal strip extending through the short groove. The cover.plates are shaped so. that a portion of each extends into and covers apart of the short. groove. Each cover plate is made so that it isinterchangeable for the other by merely turning it over. This is animportant element of the invention as it permits stamping cover platesof a single size andshape so that.

any pair of these plates can be used in any of."

the heating elements. Each cover plate; is also provided with a reducedand extended end portion1adapted to be locatedbetween the sides of thereduced and extended. ends of the groove and hold the hollow fiber glasstube in place. In the-preferred construction the outer vertical side ofeach elongated groove is provided with a flattened portion at each endthereof and atan acute angle to the remainder of the-vertical side toassist in the properlocation ofthe' coverplate. Each cover'pl'ate is,-of course, similarly shaped.

The above features of construction of the new heating element result inan element that is relatively simple and inexpensive to build and thathas an extremely longlife in use; All the electrical conductingport-ions of the heating elements are completely insulated and theentire assembly is compact and rigid so that the eleburns off at thefirst application of heat. Excellent results have been achieved by usinga starch solution for impregnating the woven fiber glass. When heatingis applied, the starch of course burns off leaving only the fiber glassand a small amount of carbon. This is not detrimental as the heat is notapplied until after the manufacturing is complete. Another impregnatingmaterial that has been used is any of various silicone resins. Theseresins being inorganic compounds are not burned off but remain on thefiber glass. The invention will be described as related to theembodiment shown in the accompanying drawings. Of the drawings:

Fig. 1 is a plan view of an electric iron sole plate with the resistanceelements in place, but omitting the insulating materials and the coverplates; Fig. 2 is a plan View of a pair of cover plates used in closingthe grooves in the sole plate shown in Fig. 1; Fig. 3 is a plan view ofa sole plate having the cover plates applied thereto with one coverplate being staked in position and the other cover. plate being merelypressed into the groove; Fig. 4 is a vertical section takensubstantially along line 4-4 of Fig. 3; Fig. 5 is an enlargedfragmentary vertical section taken substantially along line 5-5 of Fig.3; and Fig. 6 is an enlarged cross section taken through one of thefiber glass tubes and showing a resistance metal strip in place.

The heating element shown in the accompanying drawings comprises a soleplate 10 having a pair of converging elongated grooves Illa therein.Each end lllb is rounded and the outer vertical side of each groove isprovided with a fiattened portion lUc adjacent the end of the groove andarranged at an acute angle to the remainder of said side.

The converging ends of the groove IOa are connected by a short grooveHid while the diverging end of each groove is provided with a reducedand extended portion Hie.

Located within the converging grooves We are a pair of resistanceelements ll each comprising a flattened insulating core l2. Each end ofeach core is provided in a rounded configuration, as indicated at Ma,adapted to fit closely within the rounded end lflb of the groove. Theserounded portions assist in locating the core 42. The sides of the corebetween the rounded ends I2a are spaced inwardly as shown in Fig. 1.Each core I2 is wound with an elongated resistance metal strip [3, hereshown as flattened tape. A single strip is used with a portion thereofbeing wound around one core I2 and another portion being wound aroundthe other core. An intermediate portion of the strip is located withinthe short groove lOd. Each outer end of the metal strip extends througha hole or opening [21) in the corresponding rounded end [2a of the core.This arrangement aids in maintaining the coils around the core. As shownin Fig. 1, each end of each core is provided with an opening no so thateither end of the core may be located within the diverging end of thegroove.

The end of the resistance metal strip extending beyond the core [2 is inthe extended portion We of the groove and is provided with a hollow tubeM of woven fiber glass. The end of the strip extends within the interiorof the tube and this tube serves to insulate the strip from thesurrounding metal structure.

In order to prevent the outer fibers of the hollow tube 14 becomingbroken and separated during the; manufacturing operation, it ispreferred that at least the outer portion of the tube be impregnatedwith a binder. This binder may be either an organic or an inorganicmaterial and may be adapted to be either permanently associated with thetube or be burned off during the first heating of the iron. This binder,which is indicated at Ma in Fig. 6, is ordinarily applied in the form ofa solution. Excellent results have been obtained when the binder wasstarch applied in the form of a solution. This starch, of course,immediately burned off when the resistance strip became first heated.Another binder that has been used has been made of any of the well knownsilicone resins. Such a silicone resin, of course, remains permanentlyassociated with the tube.

The resistance element ll, including that portion of the resistancemetal strip located within the short groove Hid, is surrounded with aninsulating material 15 which is preferably, but not necessarily,powdered zirconium silicate. The tops of the grooves including the shortgroove Illd and the extended and reduced end portions Ifle are closed bymeans of cover plates it. As shown in Figs. 2 and 3, each cover plate isadapted to close approximately one-half of the groove. The cover platesare so shaped that either plate may be used in either groove dependingupon which surface of the cover plate is arranged as the top surface.Each cover plate is shaped similarly to a groove [0a, one-half of theshort groove Hlb and an extended portion Ifle.

In assembling the irons with the resistance elements and'the insulatingmaterial in place,

a the cover plates are arranged across the top of the grooves and aconsiderable pressure is applied to each cover plate. This pressure,which is preferably between 25 to 40 thousand pounds per square inch,serves to compress tightly the insulating material and produce what isin effect an integral structure. In Fig. 4, the cover plate at the lefthand side of the figure has been pressed down and locked in place bydisplacing the small portions of metal I01 so that these portions extendover the sides of the cover plate.

The cover plate on the right hand side of Fig. 4

has not yet been pressed down.

As shown in Fig. 5 the cover plate l6 compresses the inner portion ofthe hollow fiber glass tube It so that it assumes an oval shape. Thisserves to lock the tube in position. In a preferred constructionadditional insulating means are provided in the form of thin sheets I!of a,

separate insulating material. In the preferred construction these thinsheets are mica. As shown, one sheet I! is located on top of the tubeI4, while the other sheet is located at the bottom thereof.

The cover plate l0 may be made of a cast metal such as aluminum orsteel. When made from such a cast metal it is preferably provided withupstanding internally threaded posts l8 for use in attaching otherportions of the completed iron to the sole plate structure.

Having described our invention as related to the embodiment shown in theaccompanying drawings, it is our intention that the invention be notlimited by any of the details of this description unless otherwisespecified, but rather be construed broadly within its spirit and scopeas set forth in the accompanying claims.

We claim:

1. A heating element comprising a metal plate having an elongated groovetherein having a reduced and extended end, said groove including thereduced end projecting through the top surface of said metal plate, aresistance element in said groove having a terminal portion extendingout of said reduced end, insulating material within said groovesurrounding said resistance element,a tube comprising woven fiber glassthrough which said terminal portion of the resistance element extends,and a cover plate engaging the sides of said groove and said insulatingmaterial and having a reduced portion engaging the sides of said reducedend for holding said tube in place.

2. The heating element of claim 1 wherein a thin sheet of a separateinsulating material is provided at each of the top and bottom of saidtube within said reduced end.

3. The heating element of claim 1 wherein said tube has at least theouter portion thereof impregnated with a binder to prevent separation ofthe fibers during the manufacture of said element.

4. A heating element comprising a metal plate having an elongated groovetherein having a reduced and extended end, said groove including thereduced end projecting through the top surface of said metal plate, aresistance element in said groove having a terminal portion extendingout of said reduced end, insulating material within said groovesurrounding said resistance element, a tube comprising woven fiber glassthrough which said terminal portion of the resistance element extends,said hollow tube having at least the outer surface thereof impregnatedwith a binder to prevent separation of the fibers during the manufactureof said element, a thin sheet of mica at each of the top and bottom ofthe tube within said reduced end, and a metal cover plate engaging thesides of said groove, said insulating material and the top sheet ofmica, said plate serving to compress said tube and retain it tightly inplace.

5. A heating element comprising a metal plate having a pair ofconverging elongated grooves therein with a short groove connecting theadjacent ends of said converging grooves, the outer vertical side ofeach elongated groove being provided with a flattened portion at eachend thereof and at an acute angle to the remainder of said verticalside, and the diverging end of each elongated groove being provided witha reduced and extended end, a pair of resistance elements in saidconverging grooves including an elongated resistance metal strip locatedin said elongated grooves and extending through said short groove,insulating material surrounding said resistance elements and said stripwithin the short groove, and a cover plate in each groove extendingbetween the sides thereof and including an end portion extending intoand covering a part of said short groove, each of said cover platesbeing interchangeable with the other and the pair of cover platessubstantially completely sealing all said grooves, and each cover platebeing provided with a reduced and extended end portion to cover saidreduced and extended end of each elongated groove.

6. A heating element comprising a metal plate having a pair ofconverging elongated grooves therein with a short groove connecting theconverging ends and the diverging ends each being provided with areduced and extended end, each elongated groove having the ends thereofrounded and the outer vertical side of each groove being provided with aflattened portion at each end thereof at an acute angle to the remainderof said vertical side, a resistance element within each groovecomprising'an elongated resistance metal strip wound around'a solidcore. said core having rounded ends shaped to bear against said roundedends of said; groove and locate the resistance element within the grooveand said core having the sides thereof between said rounded ends spacedinwardly; said resistance metal strip being Wound around that portion ofthe core between said rounded ends, insulating material surroundingsaid'resistance elements and said strip within the short groove, and acover plate in each groove extending between the sides thereof andincluding anend portion extending into and covering a part of said shortgroove, each of said cover plates being interchangeable with the otherand the pair of cover plates substantially completely sealing all saidgrooves, and each cover plate being provided with a reduced and extendedend portion to cover said reduced and extended end of each elongatedgroove. 1;...

7. A heating element comprising a metal plate having an elongated groovetherein having a re duced and extended end, said groove including thereduced end projecting through the top surface of said metal plate, aresistance element in said groove having a terminal portion extendingout of said reduced end, insulating material within said groovesurrounding said resistance element, a flexible insulating tube in saidreduced end through which said terminal portion of the resistanceelement extends, and a cover plate engaging the sides of said groove andsaid insulating material and having a reduced portion engaging the sidesof said reduced end for holding said tube in place.

8. A heating element comprising a metal plate having a pair ofconverging elongated grooves therein with a short groove connecting theadjacent ends of said converging grooves, a pair of resistance elementsin said converging grooves including an elongated resistance metal striplocated in said elongated grooves and extending through said shortgroove, insulating material surrounding said resistance elements andsaid strip within the short groove, and a cover plate in each grooveextending between the sides thereof and including an end portionextending into and covering a part of said short groove, each of saidcover plates being interchangeable with the other and the pair of coverplates substantially completely sealing all said grooves, each of saidelongated grooves being provided at the diverging end thereof with areduced and extended end portion and each of said cover plates beingprovided with a similarly shaped portion for location within saidreduced and extended end portion.

CHARLES H. SPARKLIN. PHILIP J. MORE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 936,556 Newman Oct. 12. 1909 942,308 Collicott Dec. '7, 19091,520,913 Simon Dec. 30, 1924 1,979,631 Maurer Nov. 6, 1934 2,389,587Appleman Nov. 27, 1945 2,419,655 Reiser Apr. 29, 1947 2,485,672 SparklinOct. 25, 1949 2,512,220 Aske June 20, 1950 2,512,668 More June 27, 1950

